docs: def has_exact_support(m, m_hat):
      """Returns 1 if support_difference_count is zero, 0 else.
      """
      m_nnz, m_hat_nnz, intersection_nnz = _nonzero_intersection(m, m_hat)
      return int((m_nnz + m_hat_nnz - (2 * intersection_nnz)) == 0)